Normally, the two most critical stages of an aircraft flight are the takeoff and landing phases of the flight. During these phases pilot activity is higher than normal. Frequently, decisions must be rapidly made, particularly if an emergency occurs, such as the loss of power from an engine. In order to make the correct decision, it is necessary for the pilot to have available all of the information needed to make the decision. Unfortunately, in the past, aircraft instruments have not presented takeoff and landing option information to a pilot. This lack has made it difficult at times for a pilot to reach the best decision in "refused takeoff" and "landing abort" situations. In a "refused takeoff" situation, some emergency has occurred during takeoff, such as loss of power from an engine, requiring the pilot to decide if he should try to stop the aircraft or continue the takeoff. In a "landing abort" situation, the usual emergency is the aircraft landing further down the runway than normal. The pilot must decide to either stop the aircraft or apply full thrust and "go around."
In the past, proposals have been made to provide monitors for assisting pilots in reaching the correct decision in refused takeoff and landing abort situations. For various reasons, these monitors have not been widely adopted mainly because the information produced by the monitor has been incomplete and/or not displayed in an easily understood manner. Examples of prior monitors are the TOPIS airspeed situation indicator produced by Miles-Phoenix, Ltd., Church Hill, Charing Heath, Ashford, Kent, England, and a takeoff monitor proposed by Servo Mechanism, Inc., Hawthorne, Calif. The latter monitor is described in an article entitled "Takeoff Monitor Computes Runway Roll," Aviation Week, Oct. 13, 1958, pp. 99-105.
A more recent proposal that avoids many of the difficulties associated with the foregoing devices is described in U.S. Pat. No. 4,454,582, entitled "Method and Apparatus for Continuously Determining a Chronodrasic Interval" by Patrick J. Cleary et al. This patent application describes a time based system for determining the time remaining for maximum control action to be taken in order to achieve a desired objective, such as stopping or reaching rotation speed before the end of a runway. The method involves continuously determining the amount of the runway distance required to achieve rotation speed and/or stopping if maximum control action (e.g., maximum thrust or maximum braking) is applied. The method also involves continuously determining a total amount of the runway length remaining. The chronodrasic intervals are then determined by deducting the amount of runway required to achieve rotation speed and/or stopping if the related maximum control action is taken from the total amount of the runway remaining and dividing the result by a preselected rate of change. The chronodrasic interval is displayed in a manner that assists the pilot in making an informed decision regarding takeoff and stopping. The system takes into consideration various parameters associated with the aircraft.
While the method and apparatus described in U.S. Pat. No. 4,454,582, constitute a significant step forward, the resulting instrument has not been proven to be entirely satisfactory. In general, it has been shown that time domain displays of the type contemplated are not as effective in communicating information to a pilot under emergency conditions as desired. Further, the display described in U.S. Pat. No. 4,454,582, is not as informative as desired because it does not provide all of the information needed for a pilot to make an informed decision in refused takeoff and landing abort situations.